Mine too!!! They literally attatch themselves to their necks and under their bellies and chests. Terrible! I also use NAF D-ITCH and find this does work quite well and also helps to soften their skin to stop the dry, 'bitty' after effect of fly bites.
These are probably Blandford flies. They bite people too and can cause swollen ankles/feet and very large blisters. I just had a week on antibiotics after I was stung 4 times on my right ankles.
The internet claims they are associated with water - but I personally think they are associated with horses. I get bitten every year when I'm feeding/grooming my pony.
